Capacity Analysis for MIMO Two-Hop Amplify-and-Forward Relaying Systems with the Source to Destination Link

This paper presents an ergodic capacity analysis of an amplify-and-forward multiple-input, multiple-output two-hop system including the source to destination (direct) link. We first derive an expression for the probability density function of an unordered eigenvalue of the system. Then, using this result, a closed form expression for the ergodic capacity of the system is derived. The ergodic capacity expression has one integral that needs to be evaluated numerically. The results produced are valid for all SNR values and for arbitrary numbers of antennas at the source, relay and destination. We also present simulation results to validate our analysis. The results show that the analysis exactly matches the simulations and quantifies the improvements in capacity due to the diversity offered by the direct link.